Device for recognition of a pole crash

ABSTRACT

A device for recognizing a pole crash, situated in a vehicle. The pole crash is determined on the basis of an impact velocity, which is recognized by an environment sensor, and an acceleration, which occurs in upon impact and is recognized by an impact sensor. In particular, the time between the impact and the impact object hitting the engine block is determined to identify a pole crash.

BACKGROUND INFORMATION

The present invention relates to a device for detecting a pole crash.

SUMMARY

An example device according to the present invention for recognizing apole crash may have the advantage that the pole crashes are more easilyidentified. A pole crash is understood here as a crash against asmall-volume object, the structures provided for absorbing crash energynot being affected. This includes utility poles, masts, and wall edges.Pole crashes have the property that they have very small decelerationvalues in their initial phase. Due to the small impact surface and thenon-involvement of the vehicle structures designed to absorb energy,which typically include the side members up to the bumper, initiallyonly little energy is absorbed, and the pole penetrates deep into thevehicle front even at low impact velocities. Substantial decelerationdoes not occur until the pole hits the engine block. The deceleration isthen much more intense than in the case of a higher-speed impact againsta softer barrier, so that deployment of the restraining device isnecessary to protect the occupants. This prevents the two types of crashfrom being confused with one another.

According to the present invention, the impact velocity and the distancebetween the first contact point, i.e., the bumper, and the engine blockare known; therefore, it is possible to calculate the time to theinitial occurrence of the high deceleration values. This permits a polecrash to be reliably recognized and the restraining device to beaccurately controlled.

It may be particularly advantageous if the time between the moment offirst impact between the impact object and the vehicle and the momentwhen the impact object hits the engine block is measured using theimpact velocity and/or the acceleration. This may be used to identify apole crash.

Finally, it may also advantageous if the environment sensor is designedeither as a radar sensor or as an ultrasonic sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention are illustrated in thefigure and explained in more detail below.

FIG. 1 shows a block diagram of an example device according to thepresent invention.

FIG. 2 shows a diagram for illustrating a pole crash.

FIG. 3 shows a flow chart of an example method according to the presentinvention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Pole crashes are crashes in which an impact object, which initiallycauses only a slight deceleration of the vehicle, has a minimal surfacearea. In the initial phase, the acceleration signal of this crashcorresponds with that of higher-speed crashes against soft, deformablebarriers, for example, of a vehicle-vehicle crash. In some cases, theacceleration values are even lower. It is required, however, that theairbag or other restraining device does not deploy in crashes againstsoft barriers, but they must deploy in pole crashes.

According to an example embodiment of the present invention, theprocessor in the control unit which evaluates the sensor signals of asensor for detecting the impact velocity and/or a sensor for detectingthe acceleration is configured in such a way that the processor is ableto better identify a pole crash. This is advantageously possible bymeasuring the time between the moment of first impact of the impactobject against the vehicle and the moment the impact object hits theengine block. A pole crash is easily identifiable from this time viasignal analysis.

Impact object is understood here as any object which collides with thevehicle in which the device according to the present invention fordetecting a pole crash is installed. In this application, this willtypically mean a utility pole. However, it may also be any other objectcausing such a pole crash.

FIG. 1 shows an example device according to the present invention as ablock diagram. An environment sensor 1 is connected to a control unit 3via a first data input. Furthermore, an acceleration sensor 2 isconnected to a second data input of control unit 3. A processor 4running an algorithm used for recognizing a pole crash is situated incontrol unit 3. It is possible that other algorithms are run in additionto this algorithm to identify different crash types and thus to permitdeployment of restraining devices as appropriate. Control unit 3 isconnected to restraining device 5 via a data output. The restrainingdevice 5 may include, for example, airbags and/or seat belt tighteners,and/or a rollover bar. The trigger for restraining device 5 may besituated either in control unit 3 or in restraining device 5.

Only one environment sensor 1 and one acceleration sensor 2 areillustrated here as an example. It is, however, possible to use morethan one environment sensor 1 and more than one acceleration sensor 2.In the present case both sensors 1 and 2 are situated outside thecontrol unit. A unidirectional data transmission from sensors 1 and 2 tocontrol unit 3 is also provided here in particular. This line may alsobe used for powering sensors 1 and 2 from control unit 3. Environmentsensor 1 is a radar sensor or ultrasonic sensor, for example, and ispreferably installed in the front of the vehicle. It is possible toplace additional environment sensors on the vehicle body to permitcomplete environment sensing around the vehicle. Using a radar sensor orultrasonic sensor, it is possible, in particular, to determine thevelocity of an object that has been detected. Acceleration sensor 2 isused as an impact sensor, i.e., acceleration sensor 2 does not registersignificant acceleration until an impact occurs; the reduction ofvelocity may be determined from this acceleration by simple integrationand the forward displacement may be determined by double integration. Ina pole crash significant forward displacement occurs when the pole hitsthe engine block, which may be hazardous to the occupants' bodilyintegrity if the restraining device is not employed. Therefore, the useof a restraining device at an appropriate point in time is necessary inthe event of such a pole crash.

An acceleration sensor may be additionally or alternatively situated incontrol unit 3 itself. In addition to acceleration sensor 2, it is alsopossible to use other sensors for detecting an impact. Such sensorsinclude in particular deformation sensors or indirect deformationsensors, such as temperature sensors or pressure sensors. Control unit 3is typically situated at the center of the vehicle, e.g., on the vehicletunnel. It is, however, possible to associate this control unit witheach of the individual sensors, the control unit communicating, forexample via a vehicle bus, with another control unit which then triggersrestraining means 5.

FIG. 3 illustrates the algorithm running on processor 3. In method step100, sensors 1 and 2 determine the impact velocity or the accelerationwhich is occurring. The reduction in velocity and the forwarddisplacement are determined by integrating the acceleration signal. Thisprovides the particular advantage that high-frequency components arefiltered out of the signal. The forward displacement signal is the mostrobust and is to be therefore preferably used. An object of the examplemethod according to the present invention is to correctly recognize apole crash and to distinguish it from a higher-speed crash against asofter barrier, such as another vehicle. The pole crash has a smallerforward displacement at the time of deployment than the higher-speed,softer crash. As a result, the pole crash, as shown by curve 12 in FIG.2, is further above deployment threshold 13 than non-deploying,higher-speed, softer crash 11. FIG. 2 shows a distance-time diagram. Thedouble integral of acceleration is used here. Threshold 13 is a functionof the measured impact velocity.

The method is now started in method step 100 and the thresholdcomparison is carried out according to FIG. 2. Up to the moment ofdeployment, the pole crash has a smaller forward displacement than thehigher-speed, softer crash. As FIG. 2 shows, pole crash 11 is thereforefurther above deployment threshold 12 than non-deploying, higher-speed,softer crash 13. The pole crash would therefore be classified as anon-deployer. An additional deployment criterion must therefore bederived in method step 101. This discussion is based on the fact that ina pole crash significant deceleration occurs when the engine block ishit. The impact velocity and the distance between the bumper and theengine block are known, and therefore the time between the first crashcontact and the moment the pole hits the engine block may be computedusing the formula time=distance/impact velocity. Approximately at thistime, significant deceleration and significant increase in forwarddisplacement must be observed. A pole crash is then recognized and therestraining device is deployed accordingly. This makes very accuratedeployment of the restraining device possible. This comparison isperformed in method step 102, where a check is performed as to whetherthere is forward displacement at this time. If this is the case, themethod jumps to method step 103, and the restraining device 5 isdeployed accordingly. If this is not the case, the method jumps back tomethod step 100.

1. A device for recognizing a pole crash, comprising: at least oneenvironment sensor to determine an impact velocity; at least one impactsensor to determine an acceleration occurring in a crash; and aprocessor configured to detect the pole crash on the basis of the impactvelocity and the acceleration and to activate a restraining device as afunction thereof; wherein the processor is configured to determine atime between a moment of impact and a moment an impact object strikes anengine block, using the impact velocity and the acceleration, theprocessor determining the pole crash as a function of the time.
 2. Thedevice as recited in claim 1, wherein the at least one environmentsensor is a radar sensor.
 3. The device as recited in claim 1, whereinthe at least one environment sensor is an ultrasonic sensor.